Object detecting and locating system



May 3, 1949. w. w. HANSEN Er Al.

OBJECT DETECTING AND LOCTING SYSTEM 7 Sheets-Sheet 1 Filed Jan. 16, 1942vom May 3, 1949.

\ W. W. HANSEN Er AL OBJECT DETECTING AND LOCATING SYSTEM 7 Sheets-Sheet2 mbH Filed Jan. 16, 1942 .m200 Q un Il THEIR ATTORNEY 7 Sheets-Sheet 3M+ Lb' Il j W. W. HANSEN ET AL OBJECT DETECTING AND LOCATING SYSTEM May3, 1949.

Filed Jan. 1e, 1942 May 3, 1949.'

w. w. HANSEN Er AL OBJECT DETECTING AND LOCATING SYSTEM Filed Jant 16,1942 FI E-.j

jlllll/Illlllllllllll/J 7 Sheets-Sheet 4 INVENToRs: wlLLlAM w. HANSENRUSSELL H. VARIAN T R ATTORNEY May 3, 1949. w. w. HANSEN ET AL 2,468,751

OBJECT DETECTING AND LOCATING SYSTEM Filed Jan. 16, 1942 7 Sheets-Sheet5 F En Q REcElvER '6 2 '62 INPUT |-|63 I lsa-i '@(Tef) GENERATOR 6s/OUTPUT RECEIVER Y OUTPUT OUTPUT |66 RECEIVER OUTPUT 5L/ DETECTOR OUTPUTCOMMUTATOR RANsMlTTER WILLIAM W. HANSEN INVENTORS.

" BY ATTORNEY RUSSELL H. vARum May 3, 1949. w. w. HANSEN Erm.

OBJECT DETECTING AND LOCATING SYSTEM '7 Sheets-Sheet 6 Filed Jan. 16,1942 INVENToRs WILLIAM w HANSEN `RussELL H. VARIAN ATTORNEY May 3, 1949.w. w. HANSEN ET AL 2,468,151

OBJECT DETECTING AND LOCATING SYSTEM Filed Jan. 16, 1942 7 Shee'ts-Sheet'7 229 mmh 22e-f5 22 23 F I Ill-.2D F .l IST-.Z1

INVENTORS: WILLIAM W. HANSEN 252 RUSSELL H. VARIAN Patented May 3, 1949OBJECT nE'rEc'rrNG AND LocA'rING SYSTEM William W. Hansen, Garden City,and Russell H. Varian, Bellmore, N. Y., assignors to The SperryCorporation, a corporation of Delaware Application January 16, 1942,Serial No. 426,986

12 Claims. l

This invention relates, generally, to the detection and location ofobjects such as aircraft or land vehicles and the invention hasreference, more particularly. to a novel system for accomplishing thisresult. In co-pending application Serial No. 412,918, for Objectdetecting and locating system, filed September 30, 1941, in the names ofWilliam W. Hansen,A Russell H. Varian and John R. Woodyard, now PatentNo. 2,435,615,

-granted February 10, 1948, there is disclosed a system for determiningthe azimuth, elevation, radial velocity, and radial distance of anobject relative to the detecting and locating device.

The present invention accomplishes these same results by different meansand provides, inaddition, means and methods for continuously and Aautomatically centering the device on the target or other object. It isunderstood that the novel means and methods here disclosed may beutilized by one skilled in the art in conjunction with theaforementioned application to modify or broaden the scope of theprevious system.

The basic/ principles underlying the continuous wave locating systememployed in this invention are treated at length in the cited co-pendingapplication Serial No. 412,918, now Patent No. 2,435,615, grantedFebruary 10. 1948. The presence of an object in the path ofelectromagnetic radiation will cause scattering or reflection of aportion of this radiation. Some of the scattered or reflected energywill be directed back towards the source of radiation. If the object hasa comvponent of velocity relative to the power source,

the returned energy will be shifted in frequency by the Dopplerphenomenon. Since the frequency shift is directly proportional to theradial velocity, the audio frequency produced by mixing the transmittedand received frequencies in a detector located at theiradiation sourcewill be a measure of this velocity. The magnitude of this shift infrequency, given a carrier frequency of the order of A3x10g cycles persecond, is about l0 cycles per second for each mile per hour of relativevelocity along line of sight.

If an object should start from the source and move away, each time theobject progressed onehalf a transmitted wavelength, the audio beat noteor Doppler-shift frequency in the detector would pass'through one cycle.Suppose there are transmitted two slightly different frequencies whosereflections are independently received. Then the audio beat notes in theseparate detectors. will differ, in frequency in the same proportion asthe high frequencies from which they were derived. In the presentinvention, the transmitted frequencies differ so little that thefrequency dierence between their Doppler-shiftl beat notes amounts toonly a fractional cycle for each beat. This is equivalent to a slowlychanging phase shift taking place between the two 1 Doppler-shiftfrequencies as the object recedes,

and this phase difference is a measure of the distance to the scatteringobject. At a certain distance the phase shift will be one cycle, beyondwhich point the phase readings will repeat. This maximum unambiguousdistance can be changed by adjusting the frequency difference celiminated by transmitting additional frequency differences includingthe useful range of the system.

One of the objects of the present invention is to. provide a target orobject detecting and locating system wherein the means providing thepositional data of the target or object are continuously andautomatically directed at the latter.

Another object of the present invention is to provide a system of theabove character wherein, in operation, overlapping oscillating directivebeams are adapted to enclose the object within the region dei-inedbetween the central axis of the respective beams, passing through therespective radiation maxima thereof.

Another object of the present invention is to provide an objectdetecting system including directive radiator means adapted to projectelectromagnetic radiation of a plurality of frequencies and includingreceiver means having partially overlapping lobes of reception, saidsystem including servo means for orientating said radiator and receivermeans to maintain the detected object substantially on the bisector ofthe angle extending between the axes of said lobes of reception.

Still another object of the present invention is to provide a system ofthe above character having transmitter and connected radiator meanswherein impedance matching and commutating devices are employed in theline connection between the transmitter and the radiator means foralternately producing overlapping beams of electromagnetic radiation,said commutating devices comprising continuously variable capacity meanseifectively varying the line impedance.

A further object of the present invention is to provide a system of theabove character wherein impedance matching and commutating devices areemployed on concentric line means to permit energy to flow alternatelyfrom mutually adjacent antennae whose receptive spatial patterns aredisplaced slightly relative to each other resulting` in shiftingreceptive spatial patterns oscillating at the frequency of commutation.

A still further object of this invention is to the transmitter in orderto increase the output of the final detector and reduce the audio ampli-:Ilcation requirements.

A further object is to provide a cylindrical parabolic reector with apair of antennae located on either side of the focus thereof and meansto increase the interchange of energy between the antennae and thereflector so that substantially all the energy is directed by thereector whose radiation pattern is shifted by alternately energizingsaid antennae.

Still another object of this invention is to provide a system of theabove character wherein the frequencies received by intermediatefrequency amplifier means are substantially independent of the variationof transmitted carrier frequency but are determined by crystalcontrolled oscilla-A tors of the same order of magnitude as thefrequencies impressed upon said intermediate frequency amplifiers.

A still further object of the present invention is the provision of a.continuous monitoring of the received Doppler-shift frequency andautomatic follow-up by electromechanical means whereby a narrow bandfilter may be employed to discriminate against noise.

Another object is the provision of an electronic follow-up means to beutilized for the preceding object.

0ther objects and advantages will become apparent from thespecification, taken in connection with the accompanying drawingswherein the A- invention is embodied in concrete form.

Fig. 16 is a view of a part of Fig. 15 with the wave guide broken awayto reveal antennae lnside.

Fig. 17 is a sectional view of a part of Fig. 16 in greater detailshowing phase velocity modulating rods.

Figs. 1a and 19 are sectional views of one form of wave guide phasevelocity modulating rods.

Figs. 20 and 21 are sectional views of another fgixsn of wave guidephase velocity modulating r .i

Fig. 22 is a block diagram of another embodiment of the presentinvention.

Similar characters of reference are used in all of the above gures toindicate corresponding Referring now to Fig. 1, there is illustrated ina block diagram one form of apparatus for measuring the distance andradial velocity of remote objects and for automatically maintainingthedevice pointed thereat. A crystal controlled oscillatior I supplies aradio frequency to a multiplier 2. The multiplier 2 raises theoscillator frequency to an ultra high frequency which is led through a4coaxial lead I to the first hollow resonator of a final multiplier 5whose electron beam is accelerated by a battery 6. This tube is shown asa velocity modulated electron beam device of the type disclosed in U. S.Patent No. 2,242,275, for Electrical translating system and method,issued may 20, 1941, in the name of Russell H. Varian. The presentspecificationis not, however, limited to the above type, but themultiplier 5 and other tubes similarly represented may have any suitablesubstitutes. second resonator of multiplier I, tuned to a frequency f1,of the order 3 10 cycles per second, feeds its output through aconcentric line 1 to a power amplifier l. This power amplifier ismodulated with a frequency fa. of the order of, perhaps, 10* cycles persecond, by means of an audio oscillator I0 in series with the beamaccelerating voltage of a battery 9. 'Ihe output of the power amplii'ler8 is supplied to a radiator I2 through'a concentric line I I. Theradiator I2, placed at the focus of a cylindrical parabolic reflector|82, as shown in Fig. 12, forms a spatial radiatiompattern that issubstantially fanshaped. being sharply directive in azimuth and broadlydirective in elevation. This radiator may alternatively be any typecapable of producing a suitable directive beam'. such as the devicedisclosed in Fig.

4 10 of the co-pending application Serial No. 344,-

Fig, 4 illustrates an impedance matching transl former and commutator.

Figs. 5 and 6 show parts of Fig. 4 in detail.

Figs. 7 and 8 are sketches illustrating the operation of Fig. 4.

Fig. 9 shows oscillograms of wave shapes illustrating the operation ofthe present invention.

Fig. 10 is an idealized elevation view of the shifting fan beam employedin the present invention.

Fig. 11 is an idealized sectional view of the beam of Fig. 10.

Fig. 12 is an elevation view of directional radiators and antennaeemployed in the present invention.

Fig. 13 is a sectional view of a part of Fig. 12.

Fig. 14 is a sectional view of a part of Fig. 13.

Fig. 15 is an oblique view of directive wave guides employed in thepresent invention.

633 for Radiating electromagnetic wave guides and resonators, led July10, 1940, in the name of William W. Hansen. one of the presentinventors.

A wave guide radiator of this type is shown in Fig. 15 of the presentspecication where element 2M corresponds to radiator I2.

0f the frequency components issuing from radiator I2. the carrierfrequency f1 and a sideband f1 -1- la are useful to the system. Aportion of this energy leaks directly or by ground scattering toreceiving devices I3. Il.' Il, and Il'. Also, weak components due toreflection'fr'om an object or target having relative motion with respectto the equipment of this inventionrwill be received having the samefrequencies shifted slightly by the Doppler effect due to this relativemotion. Therefore, useful radiation com- Ponente f1. f1 DI. f1 -I- f2,and f1 f3 D! impinge on receiving devices I3, I3" and I4, and I4'. HereDj represents the Doppler-shift frequency, the sign being chosenpositive for an The ' frequency scale.

approaching object. These frequencies are illustrated in Fig. 3.

In this figure the approximate relative amplitudes are representedvertically, and the approximate relative positions are located on ahorizontal From left to right increasing in frequency are, first theleakage carrier f1, next the reflected Doppler-shift carrier fr-l-Dj,then the leakage upper sideband fi-i-fs, and finally the reflectedDoppler-shifted upper sideband I+3+DL Receiving antennae I3 and I3',placed on either side of the focus of a cylindrical parabolic reflector|83, as shown in Fig. 12, form partially overlapping receptive spatialpatterns that are 'substantially fan-shaped. Each of these patterns issimilar to the radiation pattern from transmitting antenna I2, beingsharply directive in azimuth and `broadly directive in elevation. 'I'heaxes of symmetry of the principal receptive lobes are equi-angularlydisplaced to either side of the azimuth axis of the locating system sothat the gain characteristics of the antennae I3 and I3' are equal alongthis azimuth axis. Fig. 10

and Fig. l1 illustrate diagrammatically these partially overlappingspatial patterns. Principal lobe |60, having an axis of symmetry 30|, isassociated with, say, antenna I3, and lobe IGI, having an axis 302, isthe gain characteristic of antenna i3'. A line 300 represents theazimuth axis of the locating system, and it will be seen to correspondto an equi-signal path.

Receiving devices I3 and I3 feed the incoming energy through concentriclines |26 and |21, respectively, to suitable energy control means shownas having the form of an ultra high frequency commutator I6. commutatorI6, driven by the shaft |44 of a motor I5, alternately connects lines|26 and |21 to an output line I1, switching inputs at a low audiofrequency f5. This commutator may be a conventional device which makesand breaks contacts mechanically, but it is preferably similar to thenovel switching means illustrated in Figs. 4-8. This latter device,utilizing the impedance transforming properties of quarter Wavelengthlines, causes the output impedances of coaxial liliesl |26 and |21 toalternate between low and substantially infinite values. This isaccomplished by connecting quarter wavelength lines to the coaxialcables |26 and |21, respectively. these coupling lines being terminatedat their free ends by variable impedances rotated by the motor I5.Constructional details and alignment procedure are disclosed when Figs.4-8 are discussed in particular.

The frequencies thus commutated are supplied through the coaxial line I1to the first resonator of mixer I8. This mixer may be electronic, asshown, or a crystal mixer may be used, if desired.

The crystal controlled oscillator I, besides controlling the transmittedfrequency, also supplies its radio frequency to a multiplier 3 where itis raised to an ultra high frequency. The output of multiplier 3 is fedby a concentric line I9 to the large resonator of a final multiplier 20.The second resonator of the multiplier 20 is tuned to a frequency fz,spaced a convenient intermediate frequency from I1. This frequencydifference is obtained by adjusting the ratio of the multipli-- cationfactors of multipliers 2 and 3. Coaxial line 2| interconnect-s thesecond resonators of multiplier 20 and mixer i8.

useful received frequencies, fr, fi-l-Df, fi-i-fa, and

fx-l-fs-i-Df to produce ,f1-f2, f'-'-fz+3. and their associated Dopplerfrequencies. Selective intermediate frequency amplifiers and detectors23 and 24 are coupled to a load 22 cf the mixer Il and are employed toamplify the Doppler frequency bands centering on the frequencies ,f1-lzand /i-fz-l-fa, respectively. In the associated detector circuit of unit23, fi-z and ,f1-f2+Dl beat together as also do fi-fa-i-ja andfi-fz-i-fs-i-Df in detector 24 to create'the Doppler-shift frequency Df.These D] voltages have a changing phase relation because of thedifference between the ultra high frequencies from which they arederived, as explained above and at greater length in the previouslymentioned co-pending application Serial No. 412,918, now Patent No.2,435,615. granted February 10, 1948.

The Df voltages of detectors 23 and 24 are fed to push-pull inputs ofbalanced modulators 25 and 26, respectively. These modulators have avariable frequency fa supplied by an audio oscillator 35 to theirparallel inputs. The push-- pull outputs of these same modulators 25 and26 connect to filters 21 and 28, respectively, suppressing the frequencyfe in a manner familiar to those skilled in the art. The audiooscillator 35 is manually, as shown in Fig. 1 for simplicity,`

or automatically, as in Fig. 1A, controlled to produce a majormodulation product of substantially' constant frequency suitable forpassing-through the narrow band filters 21 and 28. Thus, issuing fromfilters 21 and 20 are separate voltages of the same substantiallyconstant frequency whose respective phases are changing proportionallywith the phase of the Df or Doppler-shift voltages from the detectors 23and 24, respectively.

A phase comparator 29 which may be similar to the type disclosed inco-pending application Serial No. 375,373, for Phase angle indicator,filed January 22, 1941, in the name of James E. Shepherd, now Patent No.2,370,692, granted March 6, 1945, is connected to compare the phase ofthe voltage outputs of filters 21 and 28. This Phase meter 29 may becalibrated in terms of radial distance, and the audio oscillator 35,since its frequency ,fs is a function of DI, may be calibrated in termsof radial velocity of the target with reference to the locating system.Since the frequency range of the Doppler-shift voltages may be, say,5000 cycles, the employment of the filters 21 and 28, passing afrequency band of only, say, 50 cycles. greatly reduces the noise powerfed to the phase meter 29. This compression of the necessary band width,therefore, increases the sensitivity of the locating system.

Receiving antennae |`4 and |4', placed on either side of the focus of acylindrical parabolic reflector |84, as shown in Fig. |2, are identicalwith antennae |3 and |3 and reflector |63. respectively, except that theformer are arranged to be sharply directive in elevation while thelatter are sharply directive in azimuth. Receiving devices I4 and I4'for the vertical plane feed through lines |91 and |96, respectively, toan ultra high frequency commutator 30 similar to the device I6 andswitched synchronously therewith by the motor shaft |44.- The commutator30 is connected by a coaxial line 3| to a mixer 32, similar to the mixer|8, the electron beam of the former being accelerated by a battery 34.Het-" erodyning frequency f2 is supplied from the multi- 'y plier 20 bya concentric cable 33 to the second resonator of the mixer 32. Thedetected output appears across a load 36 tuned to the frequencies fi-fzand fi-fz-l-Df. This load is on the input of an I. F. amplifier anddetector 31 which corresponds i'orthe vertical plane to a device 33 fedby theload 22 for the horizontal plane. A volume indicator 33 is shownon the output of detector 38. i

Detectors 31 and 33 connect to balanced modulators 4| and 43,respectively. 'l'.'hese modulators 4| and 40, similar to modulators 25and 26, are attached to filters 43 and 42, respectively, which lattercorrespond to lters 21 and 23. The audio oscillator 35 of adjustablefrequency fe, previously mentioned, coacts with these balancedmodulaters 4| and 40 in the same manner as with lmodulators 25 and 26above. The output of illters 43 and 42 is supplied to detectors 4 5 and44, respectively, while these latter supply balanced rectiflers 48 and41, respectively. A generator 43, driven by the commutator motor I5,produces a reference voltage fs (ref.) of substantially constantmagnitude and phase which is fed by leads 43 to the rectiflers 43 and41, respectively. The output leads 303 and 334 of rectiilers 43 and 41connect to one side of single-pole double-throw switches 305 and 303,respectively. The other side of switches 305 and 306 attach to variabletaps of center grounded potentiometer-s 301 and 303, respectively,across which batteries'303 and 3|3, respectively, impress voltages; Thecenter blades of switches 305 and 303 connect to servo controlsincorporated in motors I| and 30, respectively. The servo controls maybe` polarized relays or more refined speed and direction control deviceswell known to the art. Motor 50 through gearing |39 and |14 isdesignedto turn the combined arrays I2, I3, I3', I4, and i4' and theirassociated reflectors around the vertical axis, as is shown in Fig. 12.Motor 5| through gearing |13 and |18 is arranged to rotate the samearrays around the horizontal axis, as is likewise shown in Fig. 12.

In operation if a target reilects more energy to one of the directiveantennae than to its companion antenna, the amplitude of the signals inthe receiver will be greater when the former antenna is connected by theswitching device than when the latter is connected. In other words, ifthe radiation impinging on antennae I3 and/or I4 differs in magnitudefrom the energy striking their associated units I3' and/or |'4', thecommutated frequencies fed to the mixers I3 and/or 32 and reaching I. F.amplifiers 33 aud/or 31, respectively, will be modulated at thecommutation frequency f5.

The production of the switching frequency fs may be better understood byreference to the idealized oscillograms of Fig. 9. In the graphs timeisrepresented along the horizontal axis, in-

creasing from left to right, while power or voltage is represented alongthe vertical axis, positive above and negative beneath the time axis.`The wave shapes termed Receiver input illustrate the power from a pairof antennae, say I3 and I3', that jointly` produce an oscillating beamsuch as the beam |59 of Figs. 10 and 11. The energy from the antennae iscommutated by the device I3 such as that shown in Figs. 4-8. 'I'he uppergraph illustrates power pulses |32 from the antenna I3, for example,thatis associated with the solid-line position |30 of the beam |53,while the lower graph illustrates pulses |33 from the companion antenna|3' that forms the broken line pattern |3|. The radiators arealternately energized, each being active substantially half of the timeand inactive during the period of the others activity. The squareenvelopes indicateA abrupt commutation such as may be obtained by theuse of an intermittent gear like the Geneva movement shown in Fig. 17.sinusoidal switching may be employed for mechanical simplicity althoughthe total radiation is reduced. The utilization of the former methodcauses the beam Ashown in Figs. and 11 to Jump alternately between thesmooth-line position and the dashedline position, while the lattermethod shifts the beam smoothly-from one position to the other.

, Pulses |32 from antenna I3 are larger than pulses |33 fromA antenna I3indicating, in this example, that the target lies closer to the axis 33|of the spatial pattern |30 of Figs. 10 and 11 than to the axis 332 ofthe antenna I3'. In Fig. 9 the graph termed Receiver output'representsthe envelope |34 of the intermediate frequency waves fi-f: andfi-fz-l-Dj under these conditions. Four major audio frequencycomponents, It, DI. and Dfi-fs will be present in-the detectors 33 and31 when the target is on neither horizontal nor vertical equi-signalaxis. Detectors 31 and 33 feed -Df and Dfifs to the balanced `modulators40 and 4I, respectively. The switching frequency f5 is below thecut-oil' frequency of the modulators and, therefore, may be neglected.The audio oscillator 35 also supplies the adjustable frequency fe to themodulators. Filters 42 and 43 select frequencies, Df+fs, D-i-fs-l-fs andDf-l-fs-fs from the modulator outputs and introduce them into detectors44 and 45, respectively.

These detectors reproduce fs, a phase-reversing varying-magnitude signaldue to its functional relationship to the radiation reaching antennaeI3, I3'. I4, and I4'. For example, the .Detector output" wave |35 inFig. 9 corresponds to fs in the detector 44 when the Receiver outputenvelope is |34.` However, when the target is on the right side of Figs.10 and 11 the Receiver outpu is represented by the envelope |36 and theDetector output"` wave |31 is the resulting la in the detector 44. Wave|31 is in phase opposition to |35, illustrating the fact that fareverses phase when the target crosses the axis of the locating system,Since this axis is identical with the equi-signal path, f5, drops tozero along this line. This voltage fs is ideally suited for controlpurposes when the reference voltage f5 (ret.) is

also provided. The graph marked Generator outpu illustrates thesinusoidal voltage output la (ref.) of the generator 43 drivensimultaneously with the switching process by the motor I5. This voltage|33 may be used as a reference because it has a constant magnitude and ailxed phase.

The voltage fs is supplied from detectors 44 and 45 to balancedrectifiers 41 and 43, respectively, while f5 (ref.) is brought to saidrectiers from the generator 43 by leads 43. 'I'he balanced rectiflers,well known to those skilled in the art, produce a positive or negativevoltage of varying amplitude suitable for control purposes. Balancedrectifier 41 controls the azimuth motor 50, and rectifier 43 controlsthe elevation motor 5I when switches 303 and 335 are thrown to connectleads 304 and 303, respectively, These control voltages cause the motors50 and 5|, as illustrated in Fig. 12, to rotate the arrays I3. I3' andI4, I4', respectively, for `maintaining them continuously directed atthe target. When the arrays are correctly pointed, the commutatedhalf-cycles of received radiation will be equal, the switching voltagefr will be substantially zero, and consequently the control voltagesfrom the rectiflers 41 and 43 will also be effectively zero. With no control voltage the motors 50 and 5I will be inoperative.

Inpractice the motors 50 and 5I may be manually controlled by initiallyconnecting switches 306 and 305 to variable potentiometers 308 and 301,respectively. The directive beam of radiator I2 and the directivepatterns of antennae I3, I3', I4 and I4' may be madeto sweep the sky inany desired manner by manipulation of these potentiometers. The presenceof a target in the path of the beams produces an audio note involumeindicator 39 whereupon the audio oscillator 35 is tuned to cause amaximum indication in an output meter 3H connected across the output oflter 28. The motors 50 and 5I are then placed on automatic control bythrowing switches 306 and 305 to connect leads 304 and 303,respectively,

causing the arrays to follow the movements of the l target as long asthe audio oscillator 35 is correctly tuned. The amplitude fluctuation ofthe signals in the phase comparator 29 corresponding to the lowfrequency modulation f5 may be almost completely wiped out by properlyreducing the time constant of an automatic volume control incorporatedin this comparator. The amplifier detector 23, balanced modulator 25,and lter 21 may be eliminated if desired, and the phase comparator 29may be supplied from the lter 42. The duplication of units 38, 40, and42 is for illustrative'purposes only.

Fig. 1A illustrates a somewhat modified form of the system shown in Fig.1 and employs I. F. amplifiers 23', 24' and 38', each having a fewernumber of stages than those contained in I. F. amplifiers 23, 24 and 38of Fig. 1. The structure pared inthe phase meter 29. In-parallel withvthe output of the filter v28 are placed leads 60 and sense of rotationof a motor 69 which turns a geared shaft connected to the tuning dial-1I of the audio oscillator 35.

of Fig, 1A also provides automatic control of the audio oscillator 35.For simplicityof illustration in the drawings certain parts of thesystem of Fig. 1A that are similar to parts of Fig. 1 have been omitted.

In Fig. 1A the coaxial line I9 also feeds an ultra high frequency to theflnal multiplier 20. The second resonator of this multiplier is tuned,for example, to a frequency f1|30 mc. The concentric lines 2l and 33 areshown feeding the output of the multiplier 20 to crystal mixers I8' and32. respectively, rather than to electronic mixers as shown in Fig. 1.These mixers mix the multiplier output with the energy received by theazimuthal and elevational arrays conveyed to these mixers I8' and 32through concentric lines I1 and 3|, respectively. The broad bands offrequencies about 30 mc. created in the mixers I8' and 32' are fedl toamplifiers 52 and 53 by coaxial cables 54 and 55, respectively. Theoutputs of the amplifiers 52 and 53 are connected by lines 56 and 51 tomixers 58 and 59, respectively, which latter are also supplied aheterodyne frequency of, for example, 29 mc. from a local oscillator 6Ithrough coaxial lines 62 and 63, respectively. Se.

lective intermediate frequency amplifiers 23', 24', and 38',corresponding to the unprimed elements in Fig. 1 of similar referencenumerals, take their respective frequency bands from the output of themixer 58. An amplifier 31', corresponding to the device 31 in Fig. 1, iscoupled to the mixer 59. As before, the amplifier detectors 38' and 31'are utilized in the azimuth and vertical control channels 12 and 13,respectively. Amplifier detectors 23' and 24' provide the voltages ofDoppler-shift frequency which are used in balanced modulators 25 and 26in cooperation with the audio oscillator 35 to produce the substantiallyconstant frequencies that pass through the narrow band fil- In a systememploying this modification it is merely necessary to tune theaudiooscillator 3.. in itia1ly, thereupon the switch 64 may be closed, andthe oscillator frequency will automatically track the Doppler-shiftfrequency Df to produce voltages which can pass through the narrow band21, 28 and 42, 43, which latter are embodied in azimuth control channel12 and vertical control channel 13, respectively. The action of filters65 and 66 with the balanced rectifier 61 is that of a conventionalfrequency discriminator and appears to need no further discussion.

In Fig. 1B there is illustrated an audio oscillator 35', the frequencyof which is electronically controlled. This oscillator is of the generaltype described in an article by Ginzton and Hollingsworth entitledPhase-shift oscillators, Proc. I.R.E., vol. 29, No. 2. The oscillator35' may be substituted for the devices shown between the dashed linesa-a and b-b of Fig. 1A, including the servo control 68, the motor 69,the shaft 10, and the audio oscillator 35. The device 35' contains anoscillator tube 15 having a plate load resistor 16 and a phase-shiftingnetwork in the plate to grid circuit designed to feed back a voltage ofthe proper phase and amplitude to produce oscillation at a frequencydetermined by the network parameters. The network consists of threesimilar capacity-coupled meshes and a blocking condenser 19 for thecontrol grid 80 with its grid resistor 8|. The plate of the tube 15couples through a condenser 11 to the parallel combination of a resistor18 and a tube 82. This mesh couples through a condenser 11' to theparallel impedence of a resistor 18' and a tube 82' which in turncouples to a similar mesh containing a condenser 11", a resistor 18",and a tube 82". The output of the final mesh flows through the blockingcondenser 19 and appears across me grid resistor 8l. The resistors 16and 18, 18', and 18" have one end connected to a source of platepotential 83 while the vother end is fastened to the plates of tubes 15,82, 82', and 82", respectively. The cathodes of tubes 82, 82', and 82"are grounded, but the grids are joined together and led through aresistance-capacity filter 84 to the center arm 86 of a potentiometer81. A knob 88 controls the arm 86 and taps off a negative bias voltageimpressed across the potentiometer 81 by a battery 89.

In their action the tubes 82, 82', and 82" are equivalent to variableresistors shunting the frequency determining resistors 18, 18', and 18",respectively, and equal in magnitude to the static plate resistances ofthese tubes. Since tube characteristics are a. function of the operatingpoint, the plate resistances may be adjusted over wide limits byaltering the common grid bias voltage. Thus, any change in biasconditions ters 21 and 28, respectively, and are then com- 75 will alterthe plate resistances and modify the phase-shift networks whichdetermine the fref quency of oscillator 36'. yThe oscillator isinitially tuned by knob 88. and thereafter a control f voltage isimpressed across the input leads shown cut byy broken line aa. Thisvoltage vmaintains the output frequency across ythe output leadsy fscale. f An ultra high frequency oscillator l5 supplies a generatedfrequency f1 throughy the concentric line 1 to the nrst resonator ofthek power amplifier 8. Amplifier 8 is modulated with a frequency f: orf4 from an audio oscillator lil f placed in series with thebeamaccelerating voltage 9. The rfrequency f4 may be conveniently chosengreater than fa' by vva factor of yteny to pro-y vide a decimalsubdivision of the distance scale. yIhe modulated youtput of theamplifier 8 is supplied through the concentric line to animpedancematching transformer and commutator f H6 similary tothe ydevice i8 inFig. 1 but now placed in the transmitting portion of thesystem.Radiators ||3 and H3' are alternately fed by commutator ||6 and producea shifting beam directive in.azimuth like'that illustratedv in Figs. and11.-v

yA directive antenna ||2 receives energy for supply received energy tothe impedance matclie ing transformers and commutator 38 where theswitching of lthe inputs occurs, driven by the motor l5. The commutatedenergy is fed yfrom device 3l through the coaxial cable 3|V to the mixer32 where fn is supplied as mentioned above.

V The amplier detectors 3l' and 31 areutilized in the azimuth andvertical control channels. respectively, which channels yare identical,after these units, with those shown inFlg. 1 and, consequently, need notbe discussed further.

, The modiiicationsof Figs. 1A and 1B could easily be employed in thesystem ofy Fig. 2 by one skilled in the art. The modulating frequenciesfa and f4, may be employed simultaneously, `and the phase 'comparator 29vmay be duplicated to provide continuous readings on both distancescales. f

Referring now to Fig. 4, there is rshown the commutator I8 of Fig. 1.concentric line |23 from antenna i3 connects to a line |22 through thehorizontal branchesr of av cross-#shaped yadinstable coupling |24,illustrated in liig.y 5 in greater detail. vIn a similar way theconcentric line from antenna ifconnects to ya line |23 through `the*horizontal branches of a crossi shapedadjustable coupling |28. Lines|22 and the azimuth indication and feeds it'directlyy to i the nrstresonator of the mixer i8 of Fig. 1. The

local oscillator is an ultra high frequency device 98 tuned to thefrequency fz. yThe concentrici line 2| introduces .fz from a bufferstage of the yoscillator 98 to the second resonator of the mixer I8. Theintermediate amplifiers 23y andy 24 ywith their accompanying balancedmodulator 25 and 26, audio oscillator 35, ilters 21 and 28, and phasecomparator 29 are unchanged from Fig. 1. A similar channel consisting ofan amplifier 81. a modulator 88, and a lter 88 have been added toaccommodate the new intermediate frequency band ii-jz-l-f4` andfi-fz-i-fH-Df created by the modulation frequency f4. A double-poledouble-throw switch |0| which may be coupled with the band-change switch|02 of audio oscil lator ||8 connects filter 28 or 99 to the meter 28|23 join to form the'coaxla'l cable l1 whichffeed's the mixer I3 in thereceiver section of Fig. 1. Vertical stubsof the couplings |24 and |25,projecting above the junctiony with :the horizontal f branches, containadjustable shorting plugs |28 and |28, respectively. Vertical sectionsextending below the crossing adjustably attach to lines f |3| and |32,which latter issue from shielding rboxes |33 and |34, respectively.Shafts |4|and |42, `having attached' pinions y|3'| yand |38, respec-ytively. project from the shielding boxes |33 and |34, respectively.Gears |38 and |40 on a shaft to read either the coarse or une distancescales,

respectively.

In order to maintain the oscillator 8B at a constant frequencydifference from oscillator 95, there is provided a lead |83 thattransfers some voltage of intermediate frequency from the amplifier 38to a frequency discriminator |04, a device well known in the art. Thediscriminator |84 produces a positive or negative voltage of varyingmagnitude according to the sense and number of cycles by which theoscillator 98 differs from the frequency required to maintain theintermediate frequency f1 -ja constant. This voltage controls the plateresistance of a vacuum tube |86 in series with the accelerating voltage|01 of the oscillator 86. Since the frequency of a velocity modulationoscillator is a function of its beam accelerating voltage, theoscillator 88 may be made to track the intermediate frequency althoughoscillator 85 may also vary.

The vertical control channel is unchanged from that in Fig. 1 exceptthat here the heterodyning frequency fa is supplied from the localoscillator 96 through a coaxial line |88 to the mixer 32.' The directiveantennae I4 and |4 |38 mesh with pinions |31 and |38, respectively. Agear |43 on the shaft |44 of the motor l5 engages the gear.: |40, andconsequently the shafts |4| and |42 through their associated gearing arerotated synchronously with the motor l5. Coupling |24, line |3I, box|33, shaft |4|, and gear |31 are designed to behorizontally displaceableas a unit within a wavelength of carrier frequency fr for tuningpurposesas is the combination of coupling |25, line.l |32, box |34, shaft |42,and gear |38. `The pinions |31 and |38 have lengths' adequate to allow-for these displacements. The distance between the centers of de vices|24 and |25 and the shielding boxes |33 and |34 respectively may also beadjusted by means of the slideable attachmentbetween the lower arm ofthe devices |33 and |34 and coaxial lines |3| and |32, respectively.

Fig. 5 is a detailed sectional view of the left portion of Fig. 4revealing the method of joining the coaxial lines and the interiorarrangement of the shielding box |33. The inner conductors |22', |28',and I3i' of the coaxial lines |22, |28, and |3|, respectively, arehollow and of such an interior diameter as to permit the innerconductors |24' of the device |24 to slide therein. The exteriors oflines |22, |28. and |3| are likewise enlarged to allow the exterior ofthe device |24 to slide therein. Insulating washers Mi a |41 support theinner conductors |24' coaxial with the exterior of device |24. Aninsulating washer |48 supports the inner conductor |3|'. The ratio ofthe outside diameter of conductors |24' to the inside diameter of theexterior conductor of device |24 is made substantially equal to theratio of the outside diameter of conductors |22', |26',

from the shaft |4|.

'and m' te the'mside diameter er their respee- :low shaft to facilitatelongitudinal adjustment within the upright stub of device |24. Theconductor |3I projects into the shielding box |33 where a condenserplate |49 is soldered to its end.

lThe plan view of the plate |49 is shown in Figs. "I

and 8. The other plate of the condenser may be y considered the adjacentside of the shielding box 33. The coaxial line I3| and the section ofdevice |24 below the junction, therefore, is terminated by a capacitancewhose magnitude depends on the area of the plate |49 and the spacing anddielectric constant between the plate and the side of the box |33. Theshaft |4I, driven by the motor I5 through the gears |31, |39, shaft |36,gears |48, |43 and shaft |44 as mentioned above, rotates inball-bearings |5| and spins a double-bladed chopper |52 between theplate |49 and side of the box |33. Device |52 is roughly similar to alight chopper used in motion picture art. Fig. 5 shows one of the bladesof the chopper |52 meshed as in Fig. 8. Fig. 6 is an alternate view ofthe box |33 taken at right angles to the plane of Fig. 5 looking fromthe base of the box at the end of the conductor I3 The chopper |52 maybe constructed of a high dielectric constant low loss non-conductor ormay be made of a conductor which is insulated The effect of a,non-conductor is to increase the capacity when meshed with plate |49because the dielectric constant of 'the intervening space is increased.The effect of 'an insulated conductor is to create two condensers inseries which have increased capacity due to the reduced air gaps, andthe series combination is greater than the capacity in the openposition. The shielding box |33 is dimensioned to be nonresonant to thetransmitter frequency.

The operational alignment of the commutator vI6 of Fig. 4 is simplifiedby utilizing the teaching of the Reciprocity Theorem which allows thesubstitution of an ultra high frequency oscillator in place of the mixer|8 on the end of the coaxial line I1 to provide a temporary local powersource. The alignment which is undisturbed by this substitution may beperformed by the following steps:

First, mesh the left-hand chopper |52 as in Fig. 8 and adjust the lengthof the line from the plate |49 to the center of the coupling |24 untilno energy flows down the left line |26 to the radiator I3. This meansthere is an effective short at the center of the coupling |24.

Repeat this adjustment for the right-hand side of Fig. 4.

Next, unmesh the left-hand chopper |52 as in Fig. '7 and adjust the plug|28 in the stub of the coupling |24 until therel are no standing wavesin the line |22. This means there is no reflection from the center ofthe coupling |24 and energy may flow unimpeded to the left radiator I3.

Repeat this adjustment for the plug |29.

Then, with chopper |52 meshed and the corresponding chopper in box |34unmeshed, adjust the combined lengths of the right branch of coupling|24 and line |22, until there are no standing Waves in the oscillatorline I1. 'I'his means that when the center of coupling |24 is eiectivelyshorted the oscillator" end of the line |22 ismade to appear as an opencircuit and there is no loss of power due to the short at the center ofcoupling |24.

Repeat this adjustment for the right side o Fig. 4.

Adjust the length of coaxial line |26 to the antenna I3 with the chopper|52 meshed until the line has no field present indicating that theinactive antenna I3 is absorbing no energy from space of the activeantenna I3'. This means that when the center of coupling |24 iseffectively shorted, the antenna end of the line |26 is made to appearas an open circuit, and there is no loss of radiated power from theenergized antenna I3'.

Repeat this adjustment for the right-hand line |21. 1

These above steps are repeated until the align. ment conditions aresatised. The purpose of the stub line on coupling I 24 is to couple aconjugate impedance to the center of coupling |24 which will compensate`for the fact that the chopper |52 produces only a nite change ofcapacity.

Fig. 12 illustrates a possible physical arrangement of the arrays ofFig. 1. Wheels |18 support a lplatform I1I upon which rests a rotatablepedestal |12 bearing a yoke |13. An annular. gear |14 fastened to thepedestal |12 engages a worm gear |69 on the axle of the motor 50,mentioned in reference to Fig. 1. The motor 5| of Fig. 1 is fastened tothe yoke |13 by a bracket |15. The arrays of Fig. 1' are mounted as aunit between the arms of the yoke |13 on a left trunnion |16 and a righttrunnion |11. The trunnion |11 passes through the yoke and 4serves as ashaft for a gear |18 which engages a worm gear |19 on the axle of themotor 5|. 'I'he arrays of Fig. 1 consist of similar reflectors |82 and|83 placed side by side containing the transmitting radiator I2 and thereceiving antennae I3 and I3', respectively, as well as the reflector|84, rotated in the plane of the gure with respect to the reflectors |82and |83, containing the receiving antennae I4 and I4. The reectors |82,|83, and |84, strengthened by braces I 86, are held by a frame |85. Theopenings of the reflectors are narrow rectangles while the section atright angles to the plane of Fig. 12 is parabolic as is shown in Fig.13. The reflectors are, therefore, highly directive in the plane of Fig.13 and broadly directive at right angles to this plane. The antennae |4and I4 are displaced, preferably. one-eighth wavelength to either sideof the focus of the reector |86 on the latus rectum of the parabola. Theantennae I3 and I3 are similarly located. The effect is to producedlrective spatial patterns whose axes of symmetry are not parallel tothe principal -axis of the parabola. The patterns shift as shown inFigs. 10 and 11 when first one antenna and then the other is activatedby the commutator of Figs. 4-8; Truncated cones l9| and |92, shown insection by Fig. 14, facilitateV the interchange of energy between theantennae I4 and I4 and the ree'ctor |86. Segments are cut from theportions of these truncated cones that face the mouth of the reflector.The sides of these slices are bounded by planes drawn from the focus ofthe cylindrical parabolic reiiector to its outer edges at right anglesto the reflectors flat surfaces. A cylindrical arc concentric with thefocus bounds the inner faces of the cut away parts. from the antennaewhich would spread over a wide angle and to restrict it to the reflectedbeam.

Fig. 14 shows two concentric lines with inner conductors |94 and |95 andouter conductors |96 and |91, respectively. A dielectric |98 may ll thespace between the inner and outer con- 'I'his design is to reduce directradiation ductors. The conductors |94 and lll connect with theupper'truncated conducting cone |92 while the conductors |99 and |91unfold into the lower cone |92. In the space between the cones. theconductors |94 and |99 are unshielded and. consequently, become theradiators |4'- and 4, respectively. The concentric lines. similar tolines |26 and |21 in Fig. 4, may be adjusted in length at the commutatorto make one radiator have a substantially Y'infinite input impedancewhen -the other radiator is energized and vice versa. Under theseconditions the inactive antenna does not absorb radiated energy. Thedevices in Figs. 12-14 may be interchangeably used for eitherreceptionor radiation by reason of the reciprocity theorem.

As mentioned with reference to Fig. 1 any type of radiator capable ofproducing a suitable fanshaped beam may be employed. The abonel-citedapplication Serial 190.344,633 discloses radiating electromagnetic wave'guides which may be used in place ofthe cylindrical parabolicreflectors of Figs. 12 to 14. q

Fig. 15 illustrates an alternate arrangement of Fig. 12 in part. Arotatable pedestal 200 supports a yoke 20| which has a frame 202 swungbetween the arms of the yoke on trunnions. The right trunnion 203 passesthrough the yoke arm and forms the shaft of a gear 294 which is engagedto the driving pinion 206 of a motor 201.

n the frame 202 are mounted three hollow wave guide radiators 209, 209,and 2|0 that replace reflectors |82, |83 and |94, respectively, of Fig.12. 'I'hese guides, fully discussed in the above-mentioned applicationSerial No. 344,633, especially in Fig. thereof, are constructed with twobranches disposed at an angle with respect to each other of rectangularcross-section and of a length great compared to the other dimensions.The guides have narrow longitudinal slots on the opposed f-aces of thebranches. Electromagnetic waves may be propagated from a radiator placedat the common junction or apex of the branches outwardly along theirlength at a phase velocity dependent on the cross-sectional area for agiven frequency. The radiation escapes through the slots andsubstantially none reaches the end of the guides which may be left open.The direction of propagation of the radiated waves in free space formsan angle with their direction in the hollow wave guide whose cosine isthe ratio of the phase velocity of the waves in free space to thatof thephase velocity of the waves in said guide. Thus, at a particularfrequency the two branches of a guide may be angularly adjusted to havea common direction of propagation of free space radiation-along thebisector of the angle between the branches.

Under these conditions there is obtained the fanshaped` beam desired.The wave guide 298 has an antenna situated at the :Function of Athebranches and produces a beam similar to that obtained from reilector |82and-its antenna l2 in Fig. 12.

Fig. 16 reveals a possible arrangement inside wave guides 209 and 2|0.Radiators 2|5 and 2|6 are mounted in wave guide branches 2|1 and 2 I8,respectively, equi-distant from the common junction or origin of theguide. Slots 2|! and 220 enable the radiators to be adjusted to adistance, preferably, one-eighth wave length from the origin. I'hisstructure is a development of Fig. 4 in the co-pending applicationSerial No. 367,196, now Patent No. 2,402,622, granted June 25, 1946, forRadiating Electromagnetic Wave Guides filed November 26, 1940, in thename of William W. Hansen, one of the present inventors.

In operation. the radiators, 2|5 and 2li, are arranged to be commutatedby the device of Figs. 4-8. Electromagnetic energy from the energizedantenna reaches the inactive antenna after traveliing one-quarterwavelength, resulting in a phase delay of radians. Except over the shortdistance between a. Geneva movement which is engaged to a driven 2|9 and2|6, all points in the branch containing the inactive antenna have rfromthe bisector of the angle between the branches. Fig. 6 of the citedapplication Serial No. 367,196, now Patent No. 2,402,622 granted June25, 1946 illustrates that the change in gain is more abrupt on the sideof the spatial pattern next to the bisector and less abrupt on the farside than in the case of an antenna placed at the wave guide origin. Theoscillating beam required for the systems of Figs. 1 and 2'may beproduced by commutating the antenna coaxial line inputs. The wave guidesof Fig. 15 may be interchangeably employed for transmission `orreception in a. similar manner as the devices of Figs. 12-14.

Figs. 17-21 illustrate a method of obtaining the necessary oscillatingbeam without resorting to the commutatorof Figs. 4-8. Referring to Fig.17, a radiator 225 is located atuthe junction of wave guide branches 226and 221 shown in longitudinal section. Fiat conducting rods 229 and 229,extending the length4 of the branches, are equipped with trunnions ontheir ends to permit free rotation in supports 230 and 23|.respectively. Figs. 18 and 19 show in section the positions of rods 228and 229, respectively. A drive shaft 232, seen in section, impels adriver 233 of wheel 234. A shaft 23E, seen in4 section, connects thewheel 234 to a bevel gear 231 as weil as extending beyond the plane ofthe paper to actuate a second wave guide for the other space coordinate.The gear 231 meshes with a gear 299 on a shaft 239. The rod 229 isdriven by the shaft 299 through bevel gears 242 while the rod 228 isdriven by this shaft through gears 242, 244, and 245 on shafts 240 and24|. y

In operation the rods 229 and 229 intermittently and alternately occupythe positions in the wave guides shown in Figs. 18 and 19.` Altering theposition modies the effective cross-section which results in a change ofthe phase velocity of propagation within the guide branches. Since thephase velocity of propagation in free space is constant. the directionof free space propagation must shift according to the cosine lawmentioned above relating phase velocities and directions of propagationwithin and without the radiating guide. The rods in Fig. 1 7 may bedriven smoothly without the use of the Geneva movement. In this case themechanical simplification may compensate for reduced electricalsensitivity. An alternate type of rod is shown in Figa-20 and 21corresponding to Figs. 18 and 19. Conducting rods 250 and 25|, halfround in section. alternately fit into cavities of wave guides 252`through a concentric cable to a radiator 264.

17 and 263, respectively. Here the cross-sectional area of the guide isactually reduced. whereas in Figs. 18 and 19 while the eifect is thesame it due to neld distortion.

Fig. 22 illustrates a Imodification of the present invention wherein thefrequencies received by the intermediate frequency amplifiers aresubstantially independent of the variation of the transmitted carrierfrequency but are determined by crystal controlled oscillators of thesame order of magnitude as the frequency pass bands of the intermediatefrequency amplifiers. An oscillator 260, powered by a battery 26|,generates a carrier frequency f1 of, say. 3.000 mc. A coaxial line 262interconnects the second resonator of the oscillator 266 and the firstresonator of a'power ampliiler 263 which. in turn supplies, its. outputA battery 266 accelerates the electron beam of the amplier 263. Theoscillator 266 yis furnished with a buifer stage or third resonatorwhich connects through aline 266 to a modulator tube- 261. This buiferstage prevents appreciable reaction -of the modulator upon theoscillator frequency.

The modulator 261 has a crystal controlled oscillator'266 of, say, 15mc. in series with-its accelerating battery 269. The output resonator istuned to the second upper sideband, fi+30 mc., created by the modulationof mc. on f1, and feeds through a coaxial line 210 to a illter 21| alsotuned to f1+30 mc. This filter, introduced to suppress the othermodulation products, may be a tuned ampliiler or merely a single higheiliciency resonator -which supplies a pure 114-30 mc.

by a cable 212 to a crystal mixer 213. Also entering the mixer 213 isthe received energy from antenna 214 including a leakage signal fi fromIradiator 264 and a returned signal fri-Dl from an approachingorfreceding target. Of the difference frequencies created by the mixer213, the important ones, consisting of a strong one at 30 mc. and aweaker one at 30 mc.iDf, are selected by an I. F. amplifier 216.` Afteramplification by ampliiler 216 the 30 mc. frequency and its associatedDoppler frequency are introduced into a mixer 211. A heterodyningvfrequency of 30 mc.|.455 mc., created by the interaction of the secondharmonic of 15 mc. from the modulation oscillator 266 and a frequency of.455 mc. from another crystal controlled oscillator 216 in a mixer 216,is supplied to the mixer 211. The output of the mixer 211 is a second I.F. band at .455 mc., a frequency low` enough to afford adequateselectivity in a connected amplifier 280. The second I. F. selectiveamplier 260 feeds a mixer 26| where the incoming carrier is furtherreduced to 11 kc. by beating with the input from a local crystaloscillator 282 generating .444 or .466 mc. The output of the mixer 23|is 11 kc. and 11 kazthe Doppler-shift frequency.v 'I'he sign is positivefor approaching and negative for receding targets and the shift variesfrom zero to perhaps 5,000 cycles per second. Two ampliners 283 and 264are connected to the output of the mixer 28|-, the former having a bandwidth from 6 to 11 kc. and the latter having a band width from 1'1 to 16kc. The amplifiers 263 and 264 have' a sharp cut oif at 11 kc. to nlteroutk the carrier. A double-pole double-throw switch 266 connects eitherampliier 264 or 286 to a detector circuit 261'according to whether it isdesired to detect approaching or receding targets.

' be incorporated into the distance measuring' vand I tector.

Fig. 22 illustrates a simple detecting :system suitable for directingsearchlights and similar uses, but it is understood that the vprinciplesmay follow-up systems of Figs. 1 and 2. Itl will be noted that the 30mc. carrier in the I. F. ampliiler 216 depends for stability only on thecrystal oscillator 266, while the .455 mc. carrier in the secondselective I F. amplifier 280 depends for stability only on the crystaloscillator 216. The' 11 kc. carrier output from mixer 26| is extremelystable because it is determined by crystal oscillators 218 and 282 andtherefore may be sharply discriminated against or eliminated by theamplifiers 263 and 284 without appreciably attenuating the nearbyDoppler-shift frequencies. This may be advantageous since the carrier iscommonly so very much larger than the returned signal from the targetthat little amplification canbe used without causing the carrier tooverload the de- -At this maximum output, the` audio or Doppler-shiftfrequency output vis usually quite small necessitating additional audioamplification. Another way to visualize this is to point out that alarge carrier and a small Doppler-shift frequency correspond to a verylow per cent modulation; consequently 'the audio output is low even ifthe detector is run at high levels. If the oscillator 288 is employed,the percentage of modulation in the detector 281 may be made an, valuedesired and much audio amplification eliminated.

Certain features of the present disclosure are claimed in divisional orcontinuation cases, such as application Serial No. 485,554, flled May 1,

' 1943, for Antenna systems, application Serial No. 499,562, filedAugust 2l, 1943, for Klystron apparatus, application Serial No. 503,759,led September 25, 1943, which is now Patent No. 2,414,100, grantedJanuary 14, 1947, for Automatic frequency control circuits, andapplication Serial No. 664,764, led April 25, `1946, for Ultra highvfrequency antenna apparatus.

As many changes could be made in the above construction and manyapparently widely diiferent embodiments of this invention could be madewithout departing from the scope thereof, it is intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a hunting sense. l

What is claimed is:

1. Apparatus for determining the positional data of remote objectshaving relative motion ,with respect to said apparatus comprising, meansfor generating electromagnetic energyof a plubeat notes with theadjustable frequency from An oscillator 268 may be used to supply acontrollable amount of 11 kc. voltage to replace the carrier if thelatter is completely suppressed.4 A

said oscillator, narrow band pass lter means for passing correspondingsidebands of said modulating means output, and indicator means connectedto said lter means for comparing the phases of said sidebands. p

2. In an object detecting and locating system, directive radiator meansadapted to project e1ec- Y t 19 t tromagnetic energy at an object,receiver means l having partially overlapping lobes of reception,

said receiver means serving to receive someenergy directly from saidradiator means andsome as reflected from the object and serving todetect ,any diiference frequency, and servo `means responsive to saiddifference frequency `for orientating said receiver means to maintain adetected object substantially `on the bisector of the angle extendingbetween the axes of symmetry of said lobesof reception.

`3.1Lnan object detecting and locating system, radlatormeans adapted toproject partially overlapping lobes of electromagnetic radiation into`space, receiver means for receiving aportion` of said radiation directlyand another portion as rek iiected from a relatively movable object,said` receiver4 means combining said directly `received radiation andsaid reected radiation to produce a beat note, and servo meansresponsive to said beat note for orientating said radiator means to lmaintain a detected object substantially on `the bisector of the angleextending between the axes of symmetry of said lobes `of radiation.`

4. -I n an object detecting andiocating system, meanslfor generatingultra high frequency electromagnetic energy. directive means forradiating said energy `into space. receiver means having partiallyoverlapping'` lobesof reception for re-` ceiving` a portion of saidenergy after reflection from an object, mixermeans, switching means4alternately supplying the energy in said lobesof l reception to saidmixer means, said mixer means serving to compare the frequencies of theradiated` and received energies, detector means for t demodulating thebeat frequencies produced `in said mixer, generator means rotated`synchronously with said switching means for producinga t 20 modulatingmeans. means for receiving a portion of the energy `projected into spaceafterl redection by a remote object, and .mixer means `supl saidenergyafter `reilection from an` object, `mixer means for comparing thefrequencies of; the ra diated energy, with the energy reflected fromsaid obJect, said comparison producingbeat notes proportionai to therelative fmotion of said object andsaid locating system,` a phasef-shiftoscillator of adjustable frequency having electron tubes associated withits frequency determining networks,

`lzialanced modulator means connected to `said mixer andoscillator meansfor mixing said beat notes `with the adjustable `frequency from saidphase-shift oscillator, narrow band pass filter means for., passingcorresponding sidebands of said modulator means output, frequencydiscriminator means tuned to the center ofthe narreference voltage,means for comparingthe outl `put voltage of said detector means and saidreference voltage as to phase and magnitude, motor means forworlentatingsaid radiating means and receiver means, and control means for saidmotor means for maintaining the detectedv object substantially on thebisector of the angle extending betweentthe axes of symmetry of saidlobes of reception.

l 5. In an object detecting and locating system,

' directive means for radiating electromagnetic en fergy into space,directive receiver means for receiving a portion of said radiated`energy after reflection from a remote object, mixer means. switchingmeans alternately supplying different portions of the received energy tosaid mixer means, said mixer means serving to compare the frequencies ofthe radiated and received energies, detector means for demodulating thefrequencies produced "in said mixer, means rotating synchronously withsaid switching means for supplying a reference voltage, means forcomparing the output voltage of said detector means with said referencevoltage as i to phase, and servomotor` means for orientating saidreceiver means, said servomotor means being controlled from said` phasecomparing means. 6. In a system for determining the positional data ofremote objects having relative motion with respect to said system, meansfor generating overlapping beams of fixed ultra high frequencyelectromagnetic energy, radiator means for projecting rsaidflxedfrequency energyinto space, oscillator means for generating anintermediate frequency, means for modulating the ultra, high frequencyby the intermediate frequency, filter means isolating a sidebandproduced by said row` band of` said filter `means forproducing a controlvoltage `proportional to the sense and amount of deviation f romthecenter frequency, saidcontrol voltage supplying a bias to the grids ofthe electron tubes in the frequency 'determining networks of saidphase-shift oscillator,` said bias determining the plate resistance ofsaid tubes i and so modifying the networksthat said oscillatorcompensates for` frequency changes in the beat `notes to maintain the`sidebandsof said `of said energy after reection Vfrom an object,

mixer means for comparing thefrequencies of the radiated and reflectedenergies; said comparison producingbeat notes proportional to therelative motion of `the object; and said detecting and locating` system,oscillator means of adjustable frequency, balanced modulator meansconnected to said mixer and oscillator means for mixing said beat noteswith said adjustable frequency, narrow band pass ltermeans for passing asingle sideband of` said modulator ,means` output, frequencydiscriminator means fedby said filter means, and follow-up meanscontrolled by said discriminator means for tracking-the adjustablefrequency of `said oscillator with said beat notes to maintain thesideband `of said modulator means output substantially constant. l 9.In` apparatus of the character described, directive receiver means `forreceiving continuous wave ultra high frequency energy, said receivermeans having partially overlappingzones of reception, means foralternately varying `the pick-up sensitivitylof said receivermeanssothat the lat- 2l v10. In apparatus ofthe character described,directive radiator means for radiating continuous wave ultra highfrequency energy, said radiator means having partially overlapping zonesof radiation, means for alternately varying the direc.

tivity of said radiator means so that the latter alternately radiatesmore in one zone and then radiates more in the other zone, means forreceiving a portion of said radiation after reection from a remoteobject and connected detector means for detecting amplitude variationo'f the received radiation as the directivity ofv the radiator means isvaried, generating means operable in synchronism with said directivityvarying means for supplying a reference voltage, and means 'connected tosaid detector and generating means for comparing as to phase saidreference voltage with the voltage produced by said amplitude variation.1

11. In apparatus of the character described, directive receiver meansfor receiving continuous wave-ultra high frequency energy, said receivermeans having a periodically shifting zone of reception so that it isperiodically more sensitive to column 1o, inem, .fier the werd "bmi"ummm;-

some of said energy as reected from an object, mixer means suppliedbysaid antenna means for comparing the frequencies of` the radiated andreflected energy to produce a Doppler beat note, energy control meansfor amplitude modulating the energy supplied by said antenna means tosaid mixer means by causing the energy received from one directionalternately to increase and decrease andconversely and simultaneouslycausing the energy from another direction a1- ternately to decrease andincrease, detector means for demodulating said beat note, meanssynchronized with said energy control means for producing a referencewave, and means for comparing the output of said detector means with thereference wave to obtain directional information.

WILLIAM W. HANSEN. RUSSELL H. VARIAN.

REFERENCES CITED UNITED STATES PATENTS energy originating in onedirection and then more 26 Numb@r Name Date sensitive to energyoriginating in another direc- 114501966 me] ADL 19 1923 tion, detectormeans fed by said receiver means 114671154 Hammond sept. 4 1923 fordetecting amplitude `-diierence between the 11876346 Purington sept. 131932 energies originating in different directions, gen- 2 155,206 TramADL 18 1939 erating means operable in synchronism with the' 36 ,2176 469Moueix oct. 17' 1939 shifting of said zone of reception for supplying2183399 Heismg e Dec 12 1939 a reference voltage, and means connected tosaid 2189519 Hershbeer Feb. 6 1940 detector and generating means forcomparing as 2:167'616 Gerhard Jam 16 19,19 to phase said' referencevoltage with the voltage 211931361 Rice M1111 12, 19,16 produced by saidamplitude difference. 35 2,231,929 Lyman Fb. 18, 1941 12. In an objectdetecting and locating system. 2,236,393 Chmee Apr, 1, 1941 means forgenerating electromagnetic energy. 2,253,501 Barrow Aug. 26, 1941 means`i'or radiating the energy into space, an- 2,273,447 0h] Feb, 17, 1942tenna means for receiving some of-said energy 2,409,448 Rost Oct. 15,1946 radiated directly to said antenna means and also 40 wenn ofCorrection Y remt Namens: l May 3.1040

4 WILLIAM w.. HANSEN Eran. It is hereby certied that error appears theprinted specification of the above numbered potent correction asfollows:`

and that the said Letters Patent should be read with this correctiontherein that the same may conform to the record of the case the PatentOiice.

Signed and sealed this Znd'day of May, D. 1950.

'rn'oms F. MURPHY,

